Electric controller for heating elements



Jan. 19, 1954 T E E 2,666,836

ELECTRIC CONTROLLER FOR HEATING ELEMENTS Filed Sept. 5, 1950 3 Sheets-Sheet 1 IN VEN TOR THEODOR STIEBH I BY 0 I ATTORNEY Jan. 19, 1954 T. STIEBEL ELECTRIC CONTROLLER FOR HEATING ELEMENTS Filed Sept. 5. 1950 3 Sheets-Sheet 2 FIG. 5

NTOR.

500 0WTIEBEL ATTORNEY T. STIEBEL ELECTRIC CONTROLLER FOR HEATING ELEMENTS Jan. 19, 1954 s Sheets-Shet 3 Filed Sept. 5, 1950 FIG. 6

FIG. 7

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L w m5 M N N m M m T 0 Tr D A 0, E H T Patented Jan. 19, 1954 UNITED STATES PATENT OFFICE ELECTRIC CONTROLLER FOR HEATING ELEMENTS Theodor Stiebel, Holzminden, Germany Application September 5, 1950, Serial No. 183,160 7 9 Claims.

connectableto the-supplycireuit individually or jointly. Operation .;of the step switch isat the discretion of the user; In the latter; type, the current is periodically connected and disconnected according to-its consumption. Heretofore this has beerrlper-formed manually or by specially devised apparatus operating independently of the heat condition of the heating .element. the switching sequenceis not exactly dependent on thetemperature ofithe heating element. and the particular heatingmequirements The invention relates. to a particularly simple construction of a controller for periodically con-. necting and disconnecting the'current, in which the control sequence takes place in dependence upon the particularsthermal status of the heating element. For-this purpose, a thermal probe ofv the electriccontroller is disposed in the heat ing region of the? heatingelement to transmit the effect of its heat .to the controllenwith the probeexposed tothe thermal. condition of the entire heating element; The electric controller operates automatically to interrupt the current whena definite temperature is reached, and, when the temperature of the heating element falls through a given temperature dififerential,

again to connect the supply circuit. The limitingtemperatures, at which theswitching operations of thevcontroller take place, depend on the particular construction-of the specific controller.

The construction may; be such that the heating element has but a single heating coil and the controller incorporatesa single switching device. But the construction'may also be such that the heating element has-1a plurality of circuits in which case the controller; has two switching mechanisms operating;independently of each other or in dependence upon-each other. In such construction, hwever, both of: the switching mechanisms, aregactuatedinresponse to. a

single. thermal probe-"extending into the heating. re g heofcbqth.; Gi11c11its';0;theiheal in e t 1 Both ty fis, bare the disadvantage that;

2. For independent operation, the two switching mechanisms are connected in parallel. When they operate dependent upon each other, they.

are connected serially so as the one switching mechanism disconnects the supply, the supply circuit is connected through the secondswitching mechanism.

To render the controller useful for different temperature intervals, that is to meet different.

operating requirements, there can be. inserted between the thermal probe and the switching mechanism an idling stage, the magnitude of the idling stage being variable steplessly'.

The instant invention thus results in an arrangement in which the electric controller is'so.

I in the form of an. expansion rod at the electric heating element;

Figure 2 is a horizontal section through the electrical controller and its thermal probe of Figure 1;

Figure 3 is a section along line 33 of Figure 2;

Figure 4 is a section along line 4-4 of Figure 2;. Figure 5 is a schematic drawing showing the electrical circuit of a controller of my inventionwith one heating element and one switching me chanism Figure 6 is a schematic drawing showing the electrical. connections of a controller of my invention for two heating coils and two switching mechanisms connected :in parallel, with one,

of theswitching mechanisms shown in connect stage; and

Figure? is a schematic drawing showing the its diselectrical connections of a controller of my invention for .two heating coils with the two switching mechanisms connected serially.

Referring to the drawings, in which like ref-, erence characters designate like elementsthe. heating element! of-an electric cooking. or oven plate, haszwires 35',Jserving asaheating elements, 1 embedded therein inknown manner. The'e1ec-"- 3 trical controller 2 is permanently affixed to the cooking plate, respectively the stove frame, and has a thermal probe 3. As shown in Figure 1, this probe is positioned below and across the entire length of a diameter of plate I, and comprises an outer tube affixed to the housing of the controller with a rod 4, of a material having a coefficient of expansion less than that of the tube 3. One rod end 4a is rigidly connected to the end of tube 3 remote from the controller. Within the controller housing 2, the other end of the rod 4b is welded to an elbow 9, which has a threaded bore at its free bent end to. Into the threaded bore is screwed a control pin 5, carrying an operating knob "I external the housing. Control pin 5 is additionally subjected to the effect of a compression spring 6, to prevent any accidental loosening of the control pin in the threaded bore of the elbow on vibration.

Also mounted in housing 2, a two armed lever II is positioned to pivot about an axis II), which lever in turn actuates a supplemental lever I2, rotatably mounted on pivot I2 and carrying a stop I3, made of a ceramic insulator, in which an end of an Sshaped flat spring I 4 is loosely supported. The other end of the spring I4 is mounted in a terminal I5 and carries at its mid-region a contact I6. Normally this contact I6 engages the contact I! of the current terminal connected to the heating coil. Opposite contact I! an additional contact I8 on a terminal may be disposed, positioned so that the contact it of the spring I I may engage it on the spring being snapped as hereinafter described. The terminals carrying the contacts I5, I? and I B, respectively, are rigidly mounted in insulator It and externally form the corresponding current supply terminal 26 and the current output terminal 2 I.

As shown in Figure 3, a second switching device may be provided within the controller housing 2 having elements corresponding respectively to the elements of the first switching device just described, which has as its purpose to control the current at the proper time applied to a second coil 36 (Figures 6 and 7) of the heating element.

- The electrical circuit of the controller is shown in Figure 5 from which it is readily noted that current is supplied to the heating coil 35 through one supply line terminal 31, through conductor 38, through adjustable controller 2, that is, by current supply terminal 20, spring I4, contact I6, contact I1 and current output terminal H to the coil 35, from which conductor 39 leads back to the other line supply terminal 31.

External tube 3, extending through the entire heating region of plate I, expands different amounts depending upon the different tempera tures, and at the same time, rod 4 expands correspondingly lesser amounts. This difference in the expansion of the tube and the rod is used for switching as follows: When tube 3 expands, rod 4 expanding a lesser amount is drawn slightly out of the controller housing 2. Elbow 9, being rigidly affixed to the rod, is moved carrying with it the control pin 5 screwed into the elbow. At a certain instant, control pin 5 presses against lever ll rotating it about its axis I0. Lever II thus in turn presses on lever I2, rotating the latter about its pivot I2a. Support I3 thus presses the spring I4 towards the fixed contact I5, thus tensioning the S-sh-aped spring in the longitudinal direction. At a certain instant of time, the spring suddenly snaps over, removing contact I6 from contact I1, and interrupting the circuit to the heating element suddenly and in shocklike manner. Thereafter the heating element slowly cools, tube 3 contracts, rod 4 returns into housing 2 and the control pin 5 is removed from lever II. The load is thus removed from levers I I and Ia, and spring I4 may again expand to that instant of time at which, as the result of its S-shape, it snaps over, and contacts I6 and I1 again engage each other. Thereby the circuit to the heating coil is again closed.

Undesirable stretching of spring'I I is prevented by the stop 23 which limits the rotary motion of lever I2. The instants of circuit interruption and circuit restoration may be regulated by the adjustment of knob I and pin 5 in elbow 9 as required. As clearly shown in the drawings, by appropriate adjustment of knob 1, and thus of the pin 5 in elbow 9, an idling interval of a predetermined magnitude may be introduced between pin 5 and lever I I. For example, the further the pin 5 is screwed downwardly in Figure 1, the later does the interrupting action of lever II and the switching mechanism take place, that is, the higher may the temperature of the heating element become. Also, by corresponding adjustment of knob 7, continued insertion of the controller is obtainable.

If the embodiment of the controller is such that the contact I8 is provided opposite the contact I! so that when contact IE on spring I4 leaves contact I1, it snaps to engage contact I8, various possibilities are offered. Thus a low magnitude current supply, as compared to that supplied through contact I! to the heating element, could be connected through contact I8, etc. In what is hereinafter described, I use this embodiment for the multistage form of my controller.

In the preceding, there has been described a controller having but one switching mechanism. There are advantages, however, in providing the controller initially with two adjacently positioned switching mechanisms as shown in Figures 3 and 4, the heating element I being provided with two heating coils 35 and 36. However, only one thermal probe 3 is provided and subjected to the glrect heating influence of both circuits 35 and The arrangement can be such that both switching mechanisms are connected independently, that is, in parallel to each other, and both connected to the single thermal probe. Such connection is shown in Figure 6, in which the thermal probe is provided with two elbows 9 connected through a cross member 912. An adjusting pin 5 is screwed into each elbow and each has an individual adjusting knob I. The remaining elements, I0 to I1, are each provided in duplicate. Insulating plate I6, in such construction, is provided with two additional terminals, 26 and 2 I, for the second circuit, conductor 40, heating coil 36, and conductor II. In operation, and assuming both of the springs I4 are in such position that their respective contacts I6 engage their contacts II, both heating coils 35 and 36 have current fiow ing therein. When the thermal probe correspondingly expands, the one adjusting pin 5, in accordance with its adjustment, acts to cause pressure against the one spring I 4 so that its contacts I6 and I! are removed from each other, thus causing the current flow in coil 36 to be interrupted. Thereafter heating coil 35 is operated only, until as the result of the further expansion of the thermal probe the second switching mechanism, to the left as shown in Figure 6, interrupts circuit 38, 35, 39.' Thereafter, whenelement I again cools, the latter circuit'isagain closed and saeeaaae thereaftertheformer circuit. By adjusting knobs ,1, the desired temperaturesmayberegulatedfrom case to case. a

, In the specific .embodiment of' Figure '7, the

,switchingimechanisms ..are..connected serially. Contact I8 .is connected through terminaL-IZZ toa conductor 42 which is. conne'ctedto'the second switching mechanism terminal 20. From the second switching mechanismnterminal' 2|,

conductor 43. leads to thesecond heatingcoil the embodiment of'Figure 7 .isthusr when the first switching mechanism is caused tooperate to disconnectycontact Hv on spring 14 engages .contactis in theofirst switching mechanism. ,From contact [8 the current willnow flow over conductor M! to the second switching mechanism terminal 20, over the second switching mechanism spring "It and the second switching mechanism terminal 2! and conductor 43tothe second heating coil 36, and thence vback over conductors 44 and 3S. Itwill-be noted that here again,

a single thermal probe serves for both switchingv mechanisms, and that-by suitable adjustment of knobs i the instants at which there is disconprising a hollow tube and arod within-the tube;

one end of which'is afiixed to an end ofthe tube and the other end of-which extends. beyond the other end of the tube at-room temperature, the rod having a lower coefiicient of expansion than the-tube, a housing on which'the said other end of the tube is aifixed and into which the said other end of the rod extends, and aswitching mechanism in the housing comprising anelbow of i which one arm is affixed to thesaid other :end of the rod, apin spring biased against the housing-in the other arm of the elbow, a system of levers against a first region of-which the pinis adapted to press, -a pair of terminals in the line, an S-shapedflat springv of? electrically conductive material having one end fixed in one of the pair of terminals and its other-sendpressingly bearing against. a second region of the pair of levers, the said second region being of non-conduotivemateriaLithe other terminal of. the pair engaging-thespringat its-midportion when the spring is in the preoperated position, the spring being adapted to snap into substantially its 'mirror-image' shape "on actuation to predetermined amount'inone direction by the system-of levers as'the rod on heatingwithdrawsfrom the the pin maybe adjusted to-provide a--gap of variable magnitude, including zero, between its inner end and the first region of the system of levers.

3. Electric controller according to claim 1 in which the spring biased pin in the other arm of the elbow carries a knob external the housing,

the pin being threadedfin the elbowarm, whereby the pin may. bev adjusted to provide a gaprof varij able magnitude, including zerdbetweemthe inner end of the pin and'the first region .ofQthe system of levers,and a stop on the system of levers to prevent the second region of thesystem of levers from disengaging thesaidiother end of the S- Qshaped spring.

' 4. Electric controller for heatingelementscomprisinga plurality of heating elements, an electric line supplying current to each of the plurality of heatingelements, a singlethermally responsive device adjacent thepluralityof heating elements and comprising a hollow tube and a rod within the tube one end of which ;is affixed to an endof the tube and the other end of vwhich extends. be-

, yond the other endof the tube at roomtemperature, the rod having a lower coefficient of expansion than the tuba-1 a housingto which the said other end of the tube is affixed andinto. which the said other end of the rod extends, a plurality of switching mechanisms within the housing, one switching mechanism for each of the heating elements of the plurality, a bar within the house ing afiixed to the said other end of the rod, a plurality of projections integral with the bar, one projection for each of switching mechanisms, each of the-plurality ofswitchingmechanisms comprising individual to it, a switch operating pin adjustably mountedinthe projection,. a system of levers against a first region of whichthe switch operating pin is. adapted to. press -in response to the expansion of the :rod,;,a pair of electric terminals, an S-shaped spring of electrically conductivematerial having one end fixedin one of the pair of terminalsandits otherend bearing against a. second region ofthe system of levers, the said second region beingof electrically nonconductive material, theother terminal of. the pair engaging the mid region of the .springewhen the spring is in thepreoperated position; the spring being adapted-tosnap intosubstantially its image shape on-actuation apredetermined amount in one direction by the system of levers under the pressure of the operating pin tosever the engagement between the said other terminal of the pair and themidregion of the spring and a control knob externally-the housing on the operating pin; the. pairs ofvterminals of all. the switching mechanisms being connected in paral-- lel to each other to the line,'whereby on variably positioning the respective operating pins by adjustment of theircontrol knobs, the switching mechanisms are-actuated. at different instances of time to disconnect the heating elements ofthe plurality. from the linewhen the thermally of heating elements and comprising a hollow tube and a rod within the tube one end of which is .affixed to an end of the tubeand the other end of which extends heyondthe other end of the tube at room temperature,1the.rodihaving a lower coefficient of expansion than the tube, a housing to which the said other end of the tube is affixed and into which the said other end of the rod extends, a plurality of switching mechanisms within the housing, one switching mechanism for each heating element of the plurality, a. bar within the 7 housing affixed to the said other end of the rod, a plurality of projections integral with the bar, one projection for each of the switching mechanisms, each of the switching mechanisms comprising individual to it a switch operating pin adjustably positioned in the projection, a system of levers against a first region of which the switch operating pin is adapted to press in response to the expansion of the rod, a pair of electrical terminals, an S-shaped fiat spring of electrically conductivematerial having one end fixed in one of the pair of terminals and its other end bearing against a second region of the system of levers, the said second region being of electrically nonconductive material, the other terminal of the pair engaging the midregion of the spring when the spring is in the preoperated position, the spring being adapted to snap into substantially its image shape on actuation a predetermined amount in one direction by the system of levers under the pressure of the operating pinto sever the engagement between the said other terminal of the pair and the midregion oi the spring, and a control knob externally the housing on the op erating pin, a supply of line current, the pair of terminals of one of the switching mechanisms of the plurality being connected to the line current suppy, each of the switching mechanisms in cluding the said one switching mechanism but excluding a last one of the switching mechanisms of the plurality including a third electrical terminai positioned to engage the miclregion of the spring of the respective switching mechanism when said spring is snapped into its image shape, a conductive connection from each third electrical terminal to the said one terminal of the pair of the next succeeding switching mechanism in which the said one end of the S-shaped spring of the last mentioned mechanism is fixed, whereby the supply of line current is connected successively to the successive heating elements of the plurality on disconnection of the immediately preceding heating element of the plurality at the predetermined temperatures of the thermally responsive device in accordance with the adjustment of the control pins in the projections,

6. Electric controller for heating elements comprising a plate of heat conducting material, at least one heating means embedded within the plate, a thermally responsive device adjacent the plate and comprising a hollow tube and a rod within the tube one end of which is affixed to an end of the tube and the other end of which extends beyond the other end of the tube at room temperature, the rod having a lower coeflicient of expansion than the tube, a housing on which the said other end of the, tube is affixed and into which said other end of the rod extends, and a switching means in the housing for each electrical heating means and comprising a substantially U-shapeol member of which one arm is affixed to the said other end of the rod, a pin spring biased against the housing engaging the other arm of the U-shaped member, a first pivoted lever against which the pin is adapted to press upon a predetermined motion of the said other end of the rod in the direction outwardly the housing, a second pivoted lever actuable by the first lever, an S-shaped spring of electrically conductive material, an electrical supply line, and two terminals cooperating with the S-shaped spring each of which terminals is connected to one side of the line, one end of the S-shaped spring being mechanically supported on one of the terminals while the other end thereof pressingly bears against the second lever at an electrically nonconductive portion thereof, the other terminal engaging the spring when the spring is in preoperated position and being out of engagement therewith when the spring on actuation of the second lever a predetermined amount snaps into substantially its mirror image.

7. Electric controller for heating elements according to claim 6 having a plurality of heating means embedded within the plate in which the one arm of the U-shaped member of each switching means affixed to the said other end of the rod is made common to all of the plurality of U- shaped members, and the spring biased pin of each switching means is adjustable and is adjusted to a bias corresponding to a predetermined temperature of the plate, the adjustment of each spring biased pin differing from that of each other spring biased pin.

8. Electric controller for heating elements according to claim 6 having a plurality of heating means embedded within the plate in which the one arm of each U-shaped member affixed to the said other end of the rod is made common to the plurality of U-shaped members, the spring biased pin of each switching mechanism is adjustable and is adjusted to a bias corresponding to a predetermined temperature of the plate, the adjustment of each spring biased pin differing from that of each other spring biased pin, and the two line terminals of each switching means are connected electrically in parallel.

9. Electric controller for heating elements according to claim 6 having a plurality of heating means embedded within the plate in which the one arm of each U-shaped member affixed to the said other end of the rod is made common to the plurality of U-shaped members, the spring biased pin of each switching means is adjustable and is adjusted to a bias corresponding to a predetermined temperature of the plate, the adjustment of each spring biased pin difiering from that of each otherspring biased pin, and each switching means is electrically connected in series to the other switching means of the plurality.

THEODOR STIEBEL.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,718,412 Crooker et al June 25, 1929 1,884,232 Rehm Oct. 25, 1932 1,912,921 Spencer June 6, 1933 1,963,655 Fichtner June 19, 1934 2,002,692 Dahl May 28, 1935 2,104,848 Clark Jan. 11, 1938 2,310,543 Pearce Feb. 9, 1943 2,435,530 Candor Feb. 3, 1948 2,437,262 Levitt et al Mar. 9, 1948 2,509,747 Seiter May 30, 1950 2,517,253 Spaeth Aug. 1, 1950 2,562,399 Trozmuller July 31, 1951 

